Heretofore, as methods for improving the heat and humidity resistance of a polarizer there have been known a method using dichroic dyes or polyenes as dichromophores (e.g. Japanese Patent Publication No. 5121/1986 and Patent Laid-Open no. 123944/1978) and a method wherein the surface of a dichromophore is coated with a hydrophobic resin (e.g. Japanese Patent Laid-Open No. 33612/1981 and 62011/1982).
Liquid crystal displays of TN and STN types utilizing polarizers have been used as display portions of watches and electronic calculators, and according to the recent tendency, liquid crystal displays are being applied to various uses such as, for examples, terminal displays of personal computers and word processors, displays mounted in automobiles and aircraft. The development of a polarizer superior in heat and humidity resistance and polarization characteristics is absolutely necessary for the attainment of high reliability and high picture quality of these display devices.
However, the foregoing conventional polarizers using dichroic dyes or polyenes are poor in polarization characteristics although they exhibit high heat and humidity resistance. Polarizers wherein the surface of dichromophore is coated with a hydrophobic resin such as polyurethane, polyether sulfone, polyester, or polyamide, are poor in the adhesion to polyvinyl alcohol-based polarizing elements and incapable of being rendered completely heat- and humidity-proof. Besides, interference color is easily developed due to birefringence of the hydrophobic resin layer, and curling is apt to occur due to contraction and expansion of the polarizing element and the resin layer. Thus, a limit has heretofore been encountered in the improvement of heat and humidity resistance and polarization characteristics.